Field of the Invention:
This invention relates to a novel amphoteric polyelectrolyte, a method for the production thereof, and an organic sludge dehydrater. The objects in which the amphoteric polyelectrolyte of this invention finds utility include antistatic agent for synthetic fibers, synthetic resin film, and shaped articles of synthetic resin; electroconductive agent for electrostatic recording papers and electrophotographic recording papers; yield improver for paper sheet filler; paper strength enhancer; sizing agent; polymeric flocculant and dehydrater for sewage and refuse disposal; dehydrater for various colored waste waters including stained waste water; sequestrating resin for heavy metals and ion-exchange resin; component for such cosmetic goods as hair spray; rust preventive; fungicide; mildewproofing agent; and antifoggant, for example.
Description of the Prior Art:
The amphoteric polyelectrolyte which have been known to the art include:
(1) Products obtained by Mannich reaction and the like (Japanese Patent Laid-Open SHO 58(1983)-4,898 and Japanese Patent Laid-Open SHO 58(1983)-104,299), PA0 (2) Products obtained by Hoffman reaction (Japanese Patent Laid-Open SHO 55(1980)-6,556), PA0 (3) Products containing a quanternary ammonium group or a tertiary amine group as a cationic group in the molecular unit thereof (Japanese Patent Laid-Open SHO 49(1974)-6,078 and Japanese Patent Laid-Open SHO 62(1987)-205, 112), and the amphoteric polyelectrolyte obtained by aminoalkylating reaction include: PA0 (4) Products aquated by aminoalkylating an acrylic base polymer and neutralizing the residual acid thereof with an amine (Japanese Patent Publication SHO 55(1980)-35,422), and PA0 (5) Products obtained by aminoalkylating an acrylic type base polymer with 1.0 to 1.1 equivalent weights, based on 1 equivalent weight of the acid of the base polymer, of an alkylene amine and possessing the average value of n of the suspended aminoalkyl group in the range of 1 to 1.2 (U.S. Pat. No. 3,372,149), for example.
Amphoteric polyelectrolytes have been heretofore obtained by these known techniques. Those produced by employing Mannich reaction and Hoffman decomposition reaction are not stable because of gelation, for example. An amphoteric polyelectrolyte containing mainly a quaternary ammonium group as a cationic component has been proposed as a paper strength enhancer. Though the usability of this amphoteric polyelectrolite as a flocculant is mentioned in the pertinent patent specification, the polyelectrolyte is short of fulfilling the performance expected of the flocculant. Moreover, the cationic monomer used therefor is expensive. When an amphoteric polyelectrolyte is produced by the known technique resorting to aminoalkylation, it is unstable and vulnerable to gelation.
Heretofore, the disposal of various plant effluents and the disposal of sewage and excrements have given rise to sludge of polymeric flocced and sedimented particles and excess sludge. As a dehydrater for the sludge of this type, an organic flucculant has come to find utility. In the methods for flocculation and dehydration of sludge, the method which resorts to exclusive addition of a cationic organic macromolecular flocculant and the method which resorts to simultaneous addition of a cationic organic polymeric flocculant and an anionic organic polymeric flocculant have been famous.
The method which relies on the sole addition of a cationic organic polymeric flocculant, however, is not fully effective in disposing thoroughly of the sludge and bringing about a satisfactory result in terms of cake content and speed of filtration, for example.
Further, in case of the method relying on combined use of a cationic organic polymeric flocculant and an anionic organic polymeric flocculant, though it possibly allows improvement in cake content and speed of filtration, it has a disadvantage that the operation thereof necessitates installation of a plurality of flocculant dissolving tanks and flocculant reacting tanks, the equipment therefor is expensive, and the disposal of sludge calls for heavy consumption of additives and boosts the cost of chemicals.
In recent years, a method has been proposed which uses a cationic organic macromolecular flocculant and an anionic organic macromolecular flocculant as dissolved jointly in a solution with the pH of the solution controlled as disclosed in Japanese Patent Publication SHO 60(1985)-43,800 and Japanese Patent Laid-Open SHO 58(1983)-216,706. In the case of this method, however, there is imposed a restriction on the kind of the cationic organic polymeric flocculant to be effectively usable for this method. Then, in the case of an amphoteric organic polymeric flocculant using as a cationic component thereof a monomer containing a tertiary amine or a quaternary salt as disclosed in Japanese Patent Laid-Open SHO 62(1987)-205,112, a restriction is imposed on the balance of composition of the flocculant.
When an organic polymeric flocculant containing both a cationic and an anionic component is used as an organic sludge dehydrater, the dehydrated cake content is smaller than when a cationic or an anionic flocculant is used alone as disclosed in Japanese Patent Publication SHO 60(1985)-43,800, Japanese Patent Laid-Open SHO 58(1983)-216,706, and Japanese Patent Laid-Open SHO 63(1988)-205,112. The use found for this flocculant, however, is limited.
In the case of an amphoteric organic macromolecular flocculant having as a cationic component thereof a monomer containing a tertiary amine, since the balance of composition is limited, the value of equivalent weight of cation, that of anion, and the equivalent weight ratio of cation/anion have their own limits. An amphoteric organic sludge dehydrater which combines ability of flocculation and ability of dehydration remains yet to be developed.
An object of this invention, therefore, is to provide a novel amphoteric polyelectrolyte, a method for the production thereof, and an organic sludge dehydrater using the amphoteric polyelectrolyte possessing highly satisfactory stability, a method for the production thereof, and an organic sludge dehydrater.